Certain dried, slide test elements, such as the elements available under the trademark "Ektachem" from Eastman Kodak Company, are capable of use on a variety of different analyzers. These latter include the "Ektachem 700" analyzer and the "Ektachem DT-60" analyzer, both available from Eastman Kodak Co. However, when a test element is used on one type of analyzer, e.g., one that uses one kind of reflectometer, it tends to produce a different correlation between detected response and analyte concentration, than it produces when read on a second type of analyzer, e.g., one that uses a second type of reflectometer. As a result, the correlation between detected response and concentration is different, for any given test element, when read on e.g., the "DT-60" analyzer, compared to its reading on the "Ektachem 700" analyzer.
Such different correlations require that a different calibration curve establishing the correlation, be used for each different kind of analyzer. Different calibration math has to be established for each different type of analyzer. This requires the "proper" type analyzer be used at the factory to determine the calibration, rather than any possible analyzer. Such different calibration curves and the related calibration math have to be "carried" with the test element in question such as by bar coding and/or magnetic disk. Importantly, the correction for such variation is different depending on what kind of analyzer is to be used for detection. As a result, the test elements have to be somehow segregated, using such a system, based on which type of analyzer the elements have been tested on and are destined for. In sum, the test elements have to be paired with a particular type of analyzer, especially if all or some of the calibration math is being passed along with the test elements.
Such pairings or segregation has not been a problem when there are only two basic types of analyzers to choose from, e.g., the "Ektachem 700" type and the "DT-60" type. The reason is that the "DT-60" type elements have already been packaged differently (individually) from the packaging of the "700" types (by cartridge), and the calibration math is passed differently, so that segregation occurs naturally. Where a problem arises is when yet a third type of analyzer is introduced that also packages test elements in a manner that is similar to either of the first two noted above. As a result, the test elements can end up being used on an analyzer for which the test elements bear the wrong calibration math. Keeping track of which test element is to go to what type of analyzer, and thus is to have what calibration math "carried" with it, becomes a horrendous logistics problem.
Therefore, there has been a problem prior to this invention of devising correction factors for the calibration of test elements that will not be different due to which type of analyzer the element ends up being tested on.
It is known to have a correction method that relates an aged test element to that element when fresh, or a lot-varied element of a given assay to a standard element of that assay, when always used on the same analyzer. Such a method is shown for optical density in U.S. Pat. No. 4,884,213. However, that method makes no correction for analyzer-to-analyzer variations, and furthermore incorrectly asserts that the variations that are discussed can always be corrected by a linear relationship.